Image forming apparatus

ABSTRACT

An image forming apparatus which can control to turn on/off a light emitting element depending on a sheet state on a manual sheet tray is provided. The image forming apparatus includes the manual feed tray on which the sheet is placed. The image forming apparatus is configured to be switchable between normal power mode and power saving mode. In the normal power mode, normal power is supplied. In the power saving mode, less power is consumed as compared to the power consumed in the normal power mode. The image forming apparatus includes a manual sheet feeding sensor which detects presence/absence of the sheet on the manual feed tray. The image forming apparatus includes a sheet length sensor S and a sheet length sensor L which include the light emitting element and a light receiving element to detect approximate sheet length of sheet placed on the manual feed tray in a conveying direction.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to an image forming apparatus.

Description of the Related Art

In a conventional general image forming apparatus, presence/absence of asheet (for example, a paper) is detected by a transmission-type sensorand its light shielding flag. In this arrangement, presence/absence ofsheet is detected when the transmission-type sensor respectivelyswitches between light transmitting/light shielding with an operation ofthe light shielding flag. In this method, however, it is likely that,depending on a size of the light shielding flag, the sheet cannotcorrectly be detected in a case where an edge of sheet is not in contactwith the sheet tray due to, for example, the sheet placed on the sheettray which is folded or curled.

Then, at the portion of the sheet tray where occurrence of such problemis concerned, reflection-type sensor (for example, long distance typereflection-type sensor, blank sheet detection distance of which is morethan or equal to 20 [mm]) is used to allow detection of the sheet eventhe “paper curl” is caused. The sensor of this type irradiates light ona target from light emitting element to detect reflected light. Thepresence/absence or size of the sheet is detected in this manner so thatdistance which is detectable depends on light amount of the lightemitting element. In general, light emitting diode (LED) used as thelight emitting element has a feature that the longer accumulatedlighting time of the LED gets, the less amount the LED emit lights.Further, as compared to the transmission-type sensor, the long distancetype sensor emits a larger amount of light. Thereby, due to ageddeterioration, the light amount of the LED rapidly reduces. Thus, tosuppress deterioration of the LED of the reflection-type sensor, it isnecessary to minimize the lighting time of the LED.

For example, Japanese Patent Application Laid-open No. 2003-182886discloses a device in which the reflection-type sensor as mentioned isemployed as a sensor on an original tray of an automatic documentfeeder. Also, in the device, the light emitting element is turned onjust before feeding operation is started to detect length of theoriginal and the light emitting element is turned off after thedetection.

Besides the automatic document feeder, a portion at which wrongdetection, caused by the sheet curl, is concerned in the image formingapparatus includes a manual feed tray. In the following, the differenceof sheet size detection mechanism between the automatic document feederand the manual feed tray is described.

In case of the automatic document feeder, it is less likely that thesheet is intentionally left. The original is placed on the original trayjust before reading operation of the original is started. When thereading of the original is finished, no original is left on the originaltray. That is, it is less likely that the original is left on theoriginal tray for a long time. On the other hand, in case of the manualfeed tray, a special sheet, which cannot be fed from a sheet feedingcassette, sometimes remains set intentionally on the manual feed tray.The special sheet includes postcard, envelope, etc. Due to this, it ishighly likely that the sheet is left on the manual feed tray for a longtime. For example, it is assumed that the image forming apparatus isswitchable between a normal power mode and a power saving mode. In thenormal power mode, normal power is supplied for performing imageformation. In the power saving mode, less power is consumed as comparedto the power consumed in the normal power mode. In a case where thesheet is already set on the manual feed tray when returning from thepower saving mode, sheet size is detected immediately after the returnby a sheet size sensor having a LED. Thereby, every time the imageforming apparatus returns from the power saving mode, the LED of thesheet size sensor is turned on. This results in rapid progression ofdeterioration of the LED of the sheet size sensor so that the detectiondistance is reduced, which increases the possibility that the sheet sizeis wrongly detected, which is a problem. The main object of the presentdisclosure is to provide an image forming apparatus which can controlthe turning-on of the light emitting element according to a state of thesheet on the manual feed tray.

SUMMARY OF THE INVENTION

According to the present disclosure, an image forming apparatus which isswitchable between a first mode and a second mode, in the first mode,power is supplied for performing image formation, and in the secondmode, less power is consumed as compared to the power consumed in thefirst mode, comprising: a manual feed tray on which a sheet is placed, afirst detection unit configured to detect presence/absence of the sheeton the manual feed tray; a second detection unit, including lightemitting element and light receiving element, configured to detectreflected light which is irradiated from the light emitting element bythe light receiving element and to detect an approximate sheet length ofsheet placed on the manual feed tray in a conveying direction; and acontrol unit configured to control not to turn on the light emittingelement when the image forming apparatus is switched to the first modein a case where a factor to switch the mode from the second mode to thefirst mode is a factor other than detection of sheet by the firstdetection unit.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal sectional view illustrating anexample of an image forming apparatus according to the presentembodiment.

FIG. 2 is a block diagram illustrating an example of functionalconfiguration of the image forming apparatus.

FIG. 3 is a table showing the relation between the sensor detectionresult and the sheet size.

FIG. 4 is a flowchart showing an example of the control procedureperformed by a main control unit.

FIG. 5 is a diagram illustrating an example of setting screen of sheetplaced on the manual feed tray.

FIG. 6 is a flowchart showing an example of the control procedureperformed by a driving control unit based on an instruction from themain control unit.

FIG. 7 is a cross sectional view of the manual feed tray.

DESCRIPTION OF THE EMBODIMENTS

In the following, an embodiment is described with reference to theaccompanying drawings.

FIG. 1 is a schematic longitudinal sectional view illustrating anexample of an image forming apparatus according to the presentembodiment. As shown in FIG. 1, the image forming apparatus 1 comprisesan image reading section 2 for reading an original and an image formingsection 3 for performing image formation. A platen 4, comprising atransparent glass board which is fixedly provided, is arranged on top ofthe image reading section 2 viewed from front. An original D, placed ata predetermined position on the platen 4 with its image surface orienteddownward, is pressed and fixed with an original pressing plate 5. Also,an optical system is provided on a lower side of the platen 4. Theoptical system includes a lamp 6 for illuminating the original D, andreflection mirrors 8, 9, and 10 for guiding an optical image of theilluminated original D to an image processing unit 7. It is noted thatthe lamp 6 and the reflection mirrors 8, 9, and 10 are driven by a motor(not shown), move at a predetermined speed to scan the original D.

The image forming section 3 comprises a photosensitive drum 11, aprimary charging roller 12, developing unit 13, an intermediate transferbelt 14, a transfer roller 15, a cleaner 16 and the like. Based on imagedata, an optical image is irradiated from a laser unit 17 on thephotosensitive drum 11. Then, an electrostatic latent image is formed onits surface. The primary charging roller 12 uniformly charges thesurface of the photosensitive drum 11 before irradiating laser light.The developing unit 13 adheres magenta (M), cyan (C), yellow (Y), andblack (K) toners to the electrostatic latent images formed on thesurface of the photosensitive drum 11 to form toner images. The tonerimage having developed on the surface of the photosensitive drum 11 istransferred to the intermediate transfer belt 14. The toner image havingtransferred to the intermediate transfer belt 14 is further transferredto a sheet S (for example, paper) by the transfer roller 15. The cleaner16 removes the toners remaining on the photosensitive drum 11 aftertransferring the toner images.

The sheet is supplied from a sheet cassette 18 or a manual feed tray 50.A fixing device 19 is provided on a downstream side of the image formingsection 3. The fixing device 19 fixes the toner image on the sheet beingconveyed. The sheet having the toner image fixed thereon is dischargedfrom the image forming apparatus 1 through the delivery roller pair 21.

In each sheet cassette 18, a sheet cassette open/close sensor 215 fordetecting opening and closing of the respective sheet cassettes and asheet size sensor (not shown) for detecting a size of sheet stored inthe sheet cassette are provided. Also, it is configured to automaticallydetect the size of sheet based on the output of the sheet size sensorwhen the sheet feeding cassette is closed. A manual sheet feeding sensor201 is provided on the manual feed tray 50. The manual sheet feedingsensor 201 detects presence/absence of the sheet on the manual feed tray50. The manual sheet feeding sensor 201 functions as a first detectionunit. In a case where the sheet is detected by the manual sheet feedingsensor 201, a screen to prompt a user to set the sheet size of sheetplaced on the tray is displayed on a display screen of an operation unit210. The user sets the sheet size according to the contents of thescreen displayed on the operation unit 210. In this manner, the imageforming apparatus 1 can identify the size of sheet placed on the manualfeed tray 50.

Also, the image forming apparatus 1 is configured to be switchablebetween normal power mode (first mode) and power saving mode (secondmode). In the normal power mode, normal power is supplied for performingimage formation. In the power saving mode, less power is consumed ascompared to the power consumed in the normal power mode. It means that,as the power mode, the image forming apparatus has the normal power modeand the power saving mode. In the normal power mode, the image formingapparatus 1 stands by a start of image formation while keeping supplyingpower to each load to allow immediate execution of received jobs such ascopying, printing, etc. Thereby, power consumption is large. On theother hand, in the power saving mode, the image forming apparatus 1stands by with some functions activated, including function to receiveoperation of the operation unit 210, and function to receive job such asreceiving facsimile through the network while turning off the powersupply to each load, which is unnecessary, other than the above.Thereby, as compared to the power consumed in the normal power mode,smaller power is consumed in the power saving mode. By setting time tostand by in the power saving mode as long as possible, the powerconsumption of the image forming apparatus 1 can be more reduced.

It is noted that switching of the power mode from the normal power modeto the power saving mode can be made at an arbitrary timing by pressing,by the user, a predetermined key provided on the operation unit 210.Further, the image forming apparatus 1 may be configured toautomatically switch the power mode from the normal power mode to thepower saving mode after a lapse of a predetermined time without any newprint instruction or operation from the end of printing or the end ofuser's operation.

FIG. 2 is a block diagram illustrating an example of functionalconfiguration of the image forming apparatus 1. A main control unit(CPU: Central Processing Unit) 200 mainly controls operation of theimage reading section 2, operation unit 210 and driving control unit203. The main control unit 200 mainly has a role of image processingfunction. It is noted that power is supplied to the main control unit200 from a first power source 208 when its power supply function isturned on when the image forming apparatus 1 is in both the normal powermode and power saving mode. On the other hand, the driving control unit203 mainly controls the image forming section 3. Based on an instructionfrom the main control unit 200, the driving control unit 203 performselectrophotographic process and sheet conveyance control. Also, thedriving control unit 203 has a role of forming images on the sheet basedon the information having the images processed by the main control unit200. Power is supplied to the driving control unit 203 from a secondpower source 209 when its power supply function is turned on when theimage forming apparatus 1 is in the normal power mode. It is noted that,in the power saving mode, the power supply function of the second powersource 209 is turned off.

As mentioned, when the image forming apparatus 1 is in the power savingmode, the main control unit 200 is operable, which enables to monitor astate of input signals etc. The driving control unit 203, however, isnot operable when the image forming apparatus 1 is in the power savingmode, which makes it impossible to monitor a state of input signals etc.The main control unit 200 controls switching of ON/OFF of the powersupply function of the first power source 208 and the second powersource 209. Due to this, the main control unit 200 switches the imageforming apparatus 1 to the normal power mode or power saving mode. Forexample, when the user performs an operation to switch to the normalpower mode or power saving mode through the operation unit 210, thecontrol unit 200 controls the first power source 208 and the secondpower source 209 according to the contents of the operation. Also, afront door sensor 205 detects a state of a front door which opens andcloses for replacing consumables etc. in the apparatus. Power issupplied to the manual sheet feeding sensor 201 of the manual feed tray50 and to the front door sensor 205 from the first power source 208.Thereby, even the image forming apparatus 1 is in the power saving mode,state change of the apparatus (for example, placement of sheet on themanual feed tray, open/close of the front door) can be detected.

In a case where it is detected that a state of the manual sheet feedingsensor 201 is changed from “sheet absent” to “sheet present”, the maincontrol unit 200 switches the state of the image forming apparatus 1from the power saving mode to the normal power mode. Also, in a casewhere it is detected that a state of the front door sensor 205 ischanged from “door closed state” to “door opened state”, the maincontrol unit 200 switches the state of the image forming apparatus 1from the power saving mode to the normal power mode. It is noted thatthe state of the image forming apparatus 1 can be switched from thepower saving mode to the normal power mode by, for example, pressingdown a power saving key provided on the operation unit 210. Also, theact of switching from the power saving mode to the normal power mode isreferred to as “return”.

Further, in a case where a print job is input to the image formingapparatus 1 through network, the image forming apparatus 1 isautomatically switched from the power saving mode to the normal powermode accordingly. Also, the main control unit 200 and the drivingcontrol unit 203 are configured to transfer and receive informationthrough a communication line 207 so that if the image forming apparatus1 is in the normal power mode, various information can reciprocally betransmitted and received. The output signals from the manual sheetfeeding sensor 201 and the front door sensor 205 are also input to thedriving control unit 203. Thereby, the driving control unit 203 candetect a state of each sensor when starting up the image formingapparatus 1.

Here, a description is given in detail with regard to the arrangement ofthe manual feed tray 50 with FIG. 7. The manual sheet feeding sensor 201and a sheet width sensor 211, a sheet length sensor S 212, and a sheetlength sensor L 213 for detecting a sheet size are arranged on themanual feed tray 50. The sheet width sensor 211 for detecting the sheetwidth outputs the sheet width in a direction which is vertical to sheetconveying direction as analog signals. Based on the output result, thesheet width is detected. For example, this is achieved with a variableresistor. The sheet length sensor S 212 and the sheet length sensor L213 for detecting the sheet length are the sensors arranged with fixedintervals to the conveying direction of the respective sheets. Eachsensor outputs presence/absence of the sheet as digital signals. Basedon the output result, approximate sheet length is detected. It is notedthat when it is not necessary to distinguish the sheet length sensor S212 from the sheet length sensor L 213, the sensors are referred to asthe sheet length sensor. The sheet length sensor functions as a seconddetection unit. With a combination of the detection result obtained fromthese three sensors, the sheet size is determined. In the following, aparticular description is given with FIG. 3.

FIG. 3 is a table showing the relation between the detection resultobtained from the sensors and the sheet size. As shown in FIG. 3, in thecase of A3 sheet and A4 sheet, the same values (D2, D6, D9) are obtainedfrom the sheet width sensor 211. However, the sheet length sensor L 213is configured to detect the sheet of large size, i.e., configured todetect (turn ON) only when the sheet is A3 sheet, which enables todistinguish A3 sheet from A4 sheet. It means that the sheet lengthsensor L 213 functions as a detection unit which detects that the sheetlength in the conveying direction exceeds predetermined length.

Back to the description of FIG. 2, the larger the sheet size, the morelikely that the “sheet curl” of sheet placed on the manual feed tray 50occurs. To cope with this, in the present embodiment, the sheet lengthsensor L 213 for detecting the sheet of large size is employed as areflection-type sensor. This is because the reflection-type sensor iscapable of detecting the sheet of large size even if the sheet curloccurs. The reflection-type sensor includes, for example, a lightemitting element and a light receiving element. The reflection-typesensor detects reflected light of the light irradiated from the lightemitting element by the light receiving element. In this case, powersupply to the sheet length sensor L 213 is turned ON/OFF by the drivingcontrol unit 203 and power can be supplied to the reflection-type sensordepending on a situation. It is noted that, depending on a structure ofthe manual feed tray 50, parts at which the “sheet curl” is likely tooccur vary. Thereby, the sheet length sensor S 212 can be employed asthe reflection-type sensor. Also, both the sheet length sensor S 212 andthe sheet length sensor L 213 can be employed as the reflection-typesensor.

Next, a description is given with regard to a control procedure of themain control unit 200 and the driving control unit 203 in the case wherethe image forming apparatus 1 in the power saving mode detects the sheetplaced on the manual feed tray 50 and switches to the normal power modewith FIGS. 4, 5, and 6. FIG. 4 is a flowchart showing an example of thecontrol procedure mainly performed by the main control unit 200. FIG. 5is a diagram illustrating an example of setting screen of sheet placedon the manual feed tray 50. FIG. 6 is a flowchart showing an example ofthe control procedure performed by the driving control unit 203 basedmainly on an instruction from the main control unit 200.

In response to a lapse of a predetermined time without any new printinstruction or user's operation from the end of printing processing orthe end of user's operation, the main control unit 200 switches thepower mode of the image forming apparatus 1 from the normal power modeto the power saving mode (S301). The main control unit 200 stands byuntil a factor (return factor) to switch power mode from the powersaving mode to the normal power mode occurs (S302). If it is determinedthat the return factor occurs (S302: Y), the main control unit 200shifts the power mode of the image forming apparatus 1 from the powersaving mode to the normal power mode (S303). It means that, to enablethe image formation, a power supply to the driving control unit 203 isallowed.

Here, when the image forming apparatus 1 shifts to the normal powermode, power is supplied to the driving control unit 203. Thereby, themain control unit 200 enters a state in which communication with thedriving control unit 203 is allowed. The main control unit 200 notifiesthe driving control unit 203 of the information relating to the returnfactor, for example, the information representing that a new sheet isplaced on the manual feed tray 50, representing that an open/closesensor is activated, or representing some other factor such as a userpressing a control key (S304). Also, the main control unit 200 obtainsthe information to be notified from the driving control unit 203 (S305).The main control unit 200 determines whether the information obtainedfrom the driving control unit 203 is the information including manualfeed setting request for sheet information relating to the sheet placedon the manual feed tray 50 or not. If it is determined that theinformation includes the setting request for sheet information (S306:Y), the main control unit 200 causes the display screen of the operationunit 210 to display a manual feed setting screen (described later) toprompt the user to set the sheet information (S307). The user isprompted to set the sheet information because the information relatingto the sheet placed on the manual feed tray 50 (for example, sheet size,and sheet type) is unknown. This is because the driving control unit 203is yet to confirm the information relating to the sheet placed on themanual feed tray 50. In the following, a description is given withregard to the manual feed setting screen with FIG. 5.

FIG. 5 is a diagram illustrating an example of the manual feed settingscreen displayed on the display screen of the operation unit 210. Forexample, if A4 size sheet is placed on the manual feed tray 50 by theuser, the sheet size is automatically identified by the size detectingmethod as mentioned. FIG. 5 shows a case where the sheet size of A4 sizeis identified. Thereafter, the user checks the sheet size displayed onthe manual feed setting screen, selects type of sheet etc., on thescreen, and then, presses “OK” button located right below of the screen.In this manner, the sheet information (sheet information) such as thesheet size is confirmed.

Back to the description of FIG. 4, the main control unit 200 continuesdisplaying the manual feed setting screen until the sheet information isconfirmed by the user (S308). Then, when the sheet information isconfirmed, the main control unit 200 switches the screen display fromthe manual feeding setting screen to the screen of the normal power mode(S309). On the other hand, if it is determined that the obtainedinformation includes no setting request for the sheet information (S306:N), the main control unit 200 ends a series of processing.

Also, as shown in FIG. 6, in response to the return of the image formingapparatus 1 from the power saving mode to the normal power mode, thedriving control unit 203 determines whether or not any sheet is placedon the manual feed tray 50 based on the output signals from the manualsheet feeding sensor 201 (S401). If it is determined that no sheet isplaced on the manual feed tray 50 (S401: N), the driving control unit203 ends the processing. If not, i.e., if it is determined that a sheetis placed on the manual feed tray 50 (S401: Y), the driving control unit203 verifies notification of information relating to the return factorfrom the main control unit 200 through the processing of step S304 (FIG.4) (S402). Based on the information notified from the main control unit200, the driving control unit 203 determines whether or not the returnfactor is actually due to the detection of the new sheet on the manualfeed tray 50 (S403).

If it is determined that the return factor is not derived from thedetection of the new sheet (S403: N), the driving control unit 203 endsthe processing. If not, i.e. if it is determined that the return factoris the detection of the new sheet (S403: Y), it is considered that thesheet detected on the manual feed tray 50 is not the sheet which isplaced before the image forming apparatus switches from the normal powermode to the power saving mode, but the sheet which is newly placed onthe manual feed tray 50. In this case, the driving control unit 203notifies the main control unit 200 of the determination result (S404).The processing corresponds to the processing of Step S305 (FIG. 4). Thedriving control unit 203 notifies the main control unit 200 of theinformation including the setting request of sheet.

The driving control unit 203 turns on the LED of the sheet length sensor(S405) and detects the sheet size of the sheet newly set on the manualfeed tray 50 (S406). The driving control unit 203 determines whether ornot the sheet setting is confirmed by the user (S407). It is noted thatthe driving control unit 203 continues detecting the sheet size untilthe sheet setting is completed by the user. If the sheet setting isconfirmed by the user (S407: Y), the driving control unit 203 turns offthe LED of the sheet length sensor (S408) and ends a series ofprocessing.

As mentioned, the image forming apparatus 1 according to the presentembodiment identifies the return factor by which the image formingapparatus returns from the power saving mode to the normal power mode ina case where the sheet is placed on the manual feed tray 50. Then, theimage forming apparatus 1 controls turning-on of the LED or maintainsturning-off of the LED of the sheet length sensor depending on thereturn factor identified. For example, if the return factor is thedetection of a new sheet on the manual feed tray 50, the image formingapparatus 1 turns on the LED of the sheet length sensor. Also, if thereturn factor is a factor other than the detection of the sheet on themanual feed tray 50, for example, if it is a change from “door opened”to “door closed”, the image forming apparatus 1 maintains theturning-off state of the LED. Due to this, it becomes possible tominimize the time to turn on the LED, which reduces wrong detection ofthe sheet size caused by the deterioration of the LED.

As mentioned, according to the present disclosure, by controlling theturning-on of the light emitting element depending on the state of thesheet on the manual feed tray when returning from the power saving mode,deterioration of the light emitting element can be suppressed. Thepresent invention has been described in detail by way of theabove-mentioned embodiments, but the scope of the present invention isnot limited to those embodiments.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application is a Continuation of U.S. patent application Ser. No.14/953,650, filed Nov. 30, 2015, which claims the benefit of Japanesepatent application No. 2014-248182, filed Dec. 8, 2014, which are herebyincorporated by reference herein in their entireties.

What is claimed is:
 1. An image forming apparatus which comprises powermodes having a first power mode and a power saving mode in which lesspower is consumed as compared to the first power mode, and the imageforming apparatus is configured to be switched to the first power modefrom the power saving mode, according to a predetermined factor,comprising: a sheet tray on which a sheet is placed; a feeder configuredto feed the sheet which is placed on the sheet tray, a first detectorconfigured to detect presence/absence of any sheet on the sheet tray; asecond detector, provided upstream, in a feeding direction of thefeeder, of the first detector, configured to detect presence/absence ofthe sheet on the sheet tray for determining a length of the sheet in thefeeding direction, wherein the second detector includes a light emittingelement and a light receiving element, and the light receiving elementis configured to receive light irradiated from the light emittingelement and reflected by the sheet; and a controller configured tocontrol not to turn on the light emitting element in a case where thepower mode is switched to, due to a factor other than a detection of anewly placed sheet on the sheet tray by the first detector, the firstpower mode from the power saving mode.
 2. The image forming apparatusaccording to claim 1, wherein the controller is further configured tocontrol to turn on the light emitting element in a case where the powermode is switched to, due to a detection of a newly placed sheet on thesheet tray by the first detector, the first power mode from the powersaving mode.
 3. The image forming apparatus according to claim 2,wherein the controller is further configured to allow power to besupplied to an image forming section which performs image formation in acase where the power mode is switched from the energy saving mode to thefirst mode.
 4. The image forming apparatus according to claim 1, whereinthe second detector detects presence/absence of any sheet on the sheettray to determine that the length of the sheet in the feeding directionexceeds a predetermined length.
 5. The image forming apparatus accordingto claim 1, wherein the second detector comprises a plurality of sensorsincluding the light emitting element and the light receiving element,and wherein the plurality of sensors are arranged in the conveyingdirection and each sensor outputs signals indicating presence/absence ofthe sheet.
 6. The image forming apparatus according to claim 2, furthercomprising a display configured to display a setting screen of sheetinformation including a size and type of the sheet, wherein thecontroller controls to display the setting screen on the display in acase where the power mode is switched to, due to a detection of a newlyplaced sheet on the sheet tray by the first detector, the first powermode from the power saving mode.
 7. The image forming apparatusaccording to claim 6, wherein the controller controls to continuedisplaying the setting screen and detecting presence/absence of thesheet by the second detector until the setting of the sheet informationis completed.
 8. The image forming apparatus according to claim 2,further comprising a door sensor configured to detect opening andclosing of a door included in the image forming apparatus, wherein thecontroller controls to turn on the light emitting element in a casewhere the power mode is switched to, due to a detection of a change ofthe door from a door opened state to a door closed state, the firstpower mode from the power saving mode.
 9. The image forming apparatusaccording to claim 4, wherein the second detector comprises a firstsheet sensor and a second sheet sensor, each of which is configured todetect presence/absence of the sheet placed on the sheet tray, and thesecond sheet sensor is provided upstream, in a feeding direction of thefeeder, of the first sheet sensor,
 10. The image forming apparatusaccording to claim 9, wherein the second sheet sensor is configured todetect that the sheet length in the feeding direction has a lengthlarger than the length of A4 size sheet.
 11. The image forming apparatusaccording to claim 9, wherein the first sheet sensor is configured todetect that the sheet length has a length smaller than the length of A4size sheet.
 12. The image forming apparatus according to claim 6,wherein the controller is configured to turn off the light emittingelement after completing the setting of the sheet information on thesetting screen is completed.
 13. The image forming apparatus accordingto claim 1, further comprising a printer for printing an image on asheet fed by the feeder.